French Pat. No. 1,322,927 has disclosed a method for brazing heat exchanger cores in which heating of the core is carried out by circulation of hot air through the core clamped in a mounting jig and, in order to recover calories, there is used for heating the core, some cooling air partially re-heated by having flown through a radiator core to be cooled down.
French Pat. No. 1,345,595 has disclosed an installation for brazing heat exchangers, in which the heat exchangers which are maintained in a mounting jig are caused to travel through a tunnel-oven in which hot air is blown so as to flow first through the lower portion of the heat exchanger which is then turned over so that the portion which was initially forming the higher portion becomes the lower portion and is in turn heated by an air vein flowing through it.
French Pat. No. 69-32199 concerns also brazing of heat exchangers and in this patent the heat exchangers are hung to a conveyor travelling through a tunnel-oven, the heat exchangers being displaced in the longitudinal direction of the oven, and veins of hot air being blown transversely to the longitudinal direction of the oven in order to flow through the heat exchangers and thus to heat them up to the brazing temperature.
French Pat. No. 71-29092 discloses also a brazing oven for heat exchangers, in which veins of hot air are blown across the heat exchangers, the hot air having flown through some heat exchangers being recovered in order to pre-heat other heat exchangers.
In the hereabove mentioned known publications, no account is taken of the temperature gradient existing between one and the other face of the heat exchanger.